- Not acknowledging favors; not expressing thankfulness;
unthankful; ungrateful. - Not obtaining or deserving thanks; unacceptable; as, a
thankless task.
Meaning of 'thankless' (Princeton's WordNet)
1 . thankless
[ a]
Meaning (1): - not feeling or showing gratitude
Example in sentence:
How sharper than a serpent's tooth it is / To have a thankless child!;